Bio-degradable compositions and use thereof

ABSTRACT

A method for preparing a rooting plug is disclosed. The method calls for mixing a composition comprising (i) 0.2%-10% w/w bio-degradable polymer and (ii) an organic non-hydroxylic solvent with a plug mix. The resulting method prepares a rooting plug.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/344,643, filed on Mar. 13, 2014, which is a National Phase of PCTPatent Application No. PCT/IL11/00739, filed on Sep. 18, 2011, all ofwhich are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to biodegradable compositions and their use,especially as sealants or adhesives in agriculture.

BACKGROUND

A sealant is usually used to prevent the penetration of substances orpollutants (such as air, gas, dust, fire, smoke or liquid) from onelocation through a barrier into another. Typically, desirable propertiesof sealants include insolubility, corrosion resistance, and adhesion.Sealants are used in many industries including in agriculture and inhome gardening, typically for preventing moisture from penetratingthrough barriers. For example, the inside of terra-cotta plant pots mayinclude a layer of sealant to reduce water loss from the pot.

Plant pots are commonly used by nurseries and green houses to growplants for commercial use. Plants are grown in pots until they aremature enough to be distributed to retail outlets or to consumers.Typically, molded plastic pots are used for growing plants. Consumersthat purchase plants in pots usually transplant the plants into soil attheir home, discarding the plastic pot. The pots then end up inlandfills or garbage dumps, where they remain for a very long timebecause they are not biodegradable.

Alternatives to conventional plastic pots exist. Biodegradable pots madeof paper (cellulose fibers), peat and other organic waste are known.These pots are designed to degrade relatively quickly when buried insoil. This allows consumers to simply bury the pot with the plant in it,rather than having to remove the plant from the pot before planting.However, the biodegradable pots must also be substantially resistant tosaturation by liquids so that they do not begin to disintegrate prior tobeing buried in soil.

Some biodegradable pots include a thermoplastic polymer layer whichfaces an interior of the plant pot which is exposed to soil placed inthe plant pot. However, methods of irrigation and the humid environmentin many nurseries cause the external surfaces of pots to be exposed tomoisture, so that a sealant on the interior of a plant pot does notprevent degradation of the pot while still on the shelf in the nursery.

Nurseries also use plug trays for plant transplants. In plug trays eachtransplant grows in an individual cell avoiding competition among plantsand providing uniformity of the plants. Several other advantages ofplugs (also called rooting plugs) over bare-root transplants include asmaller amount of water required for plugs over bare-root transplants, amechanical multiple-row plug transplanter can be used for planting,there is minimal root damage during transplanting and plant survival isgreater. The growing media in plug trays is typically a soilless mixgenerally made up of a combination of peat, vermiculite andhorticultural perlite and sometimes fertilizer which is packaged in athin degradable wrap. Sometimes adhesives are used for supporting andhardening the plugs.

Some commercial greenhouses use seepage irrigation (also known assub-irrigation), which is a method of irrigation that allows the soil tobe moistened from below the plants' root zone. Water is delivered frombelow, absorbed upwards, and the excess collected for recycling.Typically, a solution of water and nutrients floods a container or flowsthrough a trough for a short period of time, 10-20 minutes, and is thenpumped back into a holding tank for reuse. The bottom parts of plantpots and plugs irrigated this way are almost constantly submerged inwater.

Known bio-degradable plant pots and plugs are not suited for use withseepage irrigation systems and many other irrigation systems used ingreen houses and nurseries since they are susceptible to disintegrationwhile still in the nursery or green house due to exposure to the extrememoisture in green house and nursery environments.

SUMMARY OF THE INVENTION

Embodiments of the invention provide bio-degradable compositions thatcan be used as a sealant or adhesive for use in agriculture and homegardening and which overcome the drawbacks of known sealants. Thecompositions according to embodiments of the invention enablebio-degradation at different rates such that stability of articlescoated by these compositions can be tailored to need.

Compositions according to embodiments of the invention comprise abio-degradable polymer or co-polymer, and an organic non hydroxylicsolvent. According to one embodiment the composition comprises at leasttwo solvents, one of the solvents acting as a modifier to enhancedesired properties (e.g., elasticity) of the composition.

In one aspect of the invention there is provided a bio-degradablecomposition comprising 0.2%-10% w/w bio-degradable polymer and anorganic non hydroxylic solvent. According to one embodiment thecomposition comprises a plurality of organic non hydroxylic solvents.According to one embodiment one of the organic non hydroxylic solventsis an organic ester or a ketone.

According to some embodiments the organic non hydroxylic solvent has aboiling point of less than 80° C.

In one embodiment the bio-degradable polymer is poly lactic acid (PLA)and the organic non hydroxylic solvent is dichloromethane (DCM).

In one embodiment the composition comprises PLA, DCM and Ethyl Acetate(EtOAc). The composition may optionally include acetone.

In one embodiment the composition includes 0.2%-10% w/w PLA and up to50% DCM and up to 50% EtOAc. Some embodiments include about 0.2% w/wbio-degradable polymer. Other embodiments include about 1% w/wbio-degradable polymer. Yet other embodiments include about 2% w/wbio-degradable polymer. Some other embodiments include about 6% w/wbio-degradable polymer and yet other embodiments include about 10% w/wbio-degradable polymer.

In one aspect of the invention there is described the use of thecompositions described herein, in the preparation of a coating forbio-degradable articles.

In another aspect of the invention there is provided a method forpreparing a rooting plug, the method comprising mixing a compositionaccording to embodiments of the invention with plug mix. In oneembodiment the composition comprises 1-2% w/w bio-degradable polymer.

The method may further include creating a hollow in the plug mix andmixing the composition with the plug mix at the hollow.

In yet another aspect of the invention there is provided abio-degradable article (such as a plant pot or food-ware) which includesan article body and a coating of the article body. The coating mayinclude 0.2%-10% w/w bio-degradable polymer and an organic nonhydroxylic solvent. According to some embodiments the coating comprisesa plurality of organic non hydroxylic solvents. In one embodiment one ofthe organic non hydroxylic solvents is an organic ester or a ketone. Insome embodiments the organic non hydroxylic solvent has a boiling pointof less than 80° C.

In some embodiments the bio-degradable polymer is PLA and the organicnon hydroxylic solvent is DCM.

In some embodiments the coating comprises PLA, DCM and EtOAc. In someembodiments the coating comprises acetone

The coating may include 1%-10% w/w PLA and up to 50% DCM and up to 50%EtOAc. In one embodiment the coating comprises about 1% w/wbio-degradable polymer.

In some embodiments the article comprises more than one type of coating.In some embodiments one type of coating comprises a higher percent ofpolymer than a second type of coating.

In other embodiments the article body may be partially coated.

In another aspect of the invention there is provided a bio-degradableplant pot comprising calcium carbonate. The pot may further include acellulose containing material and optionally a starch and/or sulfatelignin and/or molasses.

The pot, according to one embodiment may include a coating, said coatingcomprising 0.2%-10% w/w bio-degradable polymer and an organic nonhydroxylic solvent.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in relation to certain examples andembodiments with reference to the following illustrative figures so thatit may be more fully understood. In the drawings:

FIG. 1 is a schematic illustration of a plant pot coated with a sealantaccording to one embodiment of the invention;

FIG. 2 is a schematic illustration of plant pot differentially coatedwith a sealant according to an embodiment of the invention;

FIG. 3 is a schematic illustration of a plug including an adhesiveaccording to embodiments of the invention; and

FIG. 4 is a schematic illustration of food ware coated with a sealantaccording to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention provide bio-degradable compositions thatcan be used as a sealant or adhesive for use in agriculture and homegardening. According to other embodiments the compositions may be usedin other fields of industry.

Compositions according to embodiments of the invention comprise abio-degradable polymer or co-polymer, and an organic non hydroxylicsolvent. According to one embodiment the composition comprises at leasttwo solvents, one of the solvents possibly acting as a modifier.

Examples of bio-degradable polymers or co-polymers that may be used incompositions according to embodiments of the invention include polylactic acid (PLA) or poly lactic-co-glycolic acid (PLGA) and typicallynaturally occurring polyesters including polyhydroxyalkanoates, such aspoly hydroxyl butyrate (PHB). Other suitable bio-degradable polymers maybe used.

Examples of solvents that may be used in compositions according toembodiments of the invention include dichloromethane (DCM),dichloroethane, tetrachloroethylene, tetrahydrochloride,dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO),organic esters such as: ethyl acetate (EtOAc), butyl acetate and ethylpropionyl, and ketons such as acetone and cyclohexanone. Other suitablesolvents may be used.

According to one embodiment compositions are prepared by mixing, in roomtemperature (about 25° C.), a polymer (possibly in the form of a resin)into a solvent or mixture of solvents until the polymer is dissolved.The mixture may then be heated to remove excess solvent. In oneembodiment the composition is heated only up to about 80° C.

According to one embodiment compositions may include a mixture ofsolvents, one solvent having a higher boiling point than the other. Forexample, DCM and EtOAc may be both used as solvents in a composition,the DCM evaporating more rapidly than the EtOAc due to its lower boilingpoint. The slower evaporating EtOAc may then enable certain propertiesof the composition to be expressed. For example, a higher percent ofEtOAc relative to DCM may be used in a composition to obtain a moreelastic coating.

Compositions resulting from the mixtures described above are fluidswhich become film-like upon drying. Compositions according toembodiments of the invention can be used for coating articles (e.g., byimmersion or by spraying) typically biodegradable articles, such asbio-degradable plant pots, bio-degradable food-ware (plates, bowels,cups and other utensils) and other suitable articles.

Bio-degradable articles, often single-use articles, are usually designedto rapidly disintegrate once buried in soil. However, when coated, therate of degradation of the coating typically determines the degradationof the whole article.

According to one embodiment compositions comprise 0.2%-10% w/w polymerin solvent. Viscosity and durability of the composition are directlyproportional to the percent of polymer in the composition.

Compositions and coatings according to embodiments of the invention canbe designed to disintegrate at different rates such that stability ofarticles coated according to embodiments of the invention, can betailored to need.

For longer durability of the coating a composition having a higherpercent of polymer may be used. According to some embodiments, severalcoat layers may be used for overall longer durability of the coating.

For example, disposable food ware, such as a plate, is expected to bekept in relatively dry conditions until it is used. During its use theplate is expected to be exposed to liquids and after its use (typically,a matter of hours) the plate is discarded. In this case, a coatingdesigned to disintegrate within hours or days of exposure to moisturemay be appropriate.

In the case of disposable plant pots, the pots are expected to be keptin a moist environment for a period of several weeks up to severalmonths prior to being discarded or being planted in soil (e.g., in thenursery or in a consumer's house prior to the plant being transferred tosoil). Once in soil (either in the garbage dump or, if relating to aplantable pot, in soil after being planted) the pot may disintegratemore rapidly. In fact, rapid disintegration of a plantable pot isadvantageous in facilitating plant growth due to release of the plant'sroots from the enclosure of the plant pot walls. Thus, according to oneembodiment, coating of plant pots is designed for several weeks' up toseveral months' durability on the shelf in a nursery but quickerdisintegration in soil.

Compositions according to embodiments of the invention enable to producea bio-degradable plant pot that can withstand extreme moistureconditions, such as the conditions prevailing in nurseries, for examplenurseries employing seepage irrigation.

Plant pots coated according to embodiments of the invention may bedifferentially coated. For example, a bottom part (floor) of a pot maybe coated with a more durable composition (e.g., higher percentage ofpolymer) than the surrounding walls of the pot or the interior of a potmay be coated with a more durable composition relative to the exteriorof the pot.

In another embodiment rooting plugs may include growth media (alsoreferred to as plug mix) mixed with a composition according toembodiments of the invention. Compositions according to embodiments ofthe invention may be used as an adhesive to produce a firmer (and thusmore easily handled) plug than currently used plugs. Plugs can bedesigned to be durable for a longer period and/or the solidity orfirmness of each plug may be designed to need based upon the specificcomposition used.

One embodiment of the invention is schematically illustrated in FIG. 1in which a bio-degradable plant pot (10) is coated with a sealantaccording to embodiments of the invention to prevent degradation of thepot while in use. According to one embodiment degradation of the sealantstarts at a pre-designed time after coating of the pot, eventuallyenabling environment friendly degradation of the whole pot.

A bio-degradable pot may be made of agriculture residues such as bamboopulp or husks, composted manure, saw dust, different starches and otherorganic, typically renewable, matter. According to one embodiment aplant pot (or other article) may be made of a mixture of calciumcarbonate (typically used in industry to entrap impurities, such as inthe sugar production industry) and sawdust or other cellulose containingmaterial. A small amount of starch, sulfate lignin or molasses is addedto the calcium carbonate-cellulose mixture to act as an adhesive. Othersuitable adhesives may be added. Water is then added to the mixture toobtain a dough-like composition that may be shaped into pots or otherarticles. The articles are then dried (possibly while heating).According to another embodiment the calcium carbonate-cellulose—adhesivemixture (or other suitable mixtures) is shaped into a pot by pressforming or by thermoforming. Other methods may be used for preparingpot.

According to one embodiment bio-degradable pots may be made of mixturecomprising 40% calcium carbonate, 40% sawdust and 20% flour. Otherpercentages of calcium carbonate and cellulose containing materials andstarch containing materials may be used.

A typical plant pot (10) includes drainage holes (11) in its bottom part(12). According to one embodiment a plant pot (10) is coated by sprayinga composition according to embodiments of the invention on it tocompletely cover the pot with a coating of composition or to partiallycover the pot. Any other suitable methods of coating may be used. Thepot is then dried in the open air until the formation of a film-likecoating (13) over all the surfaces of the pot. The pot may be driedunder other conditions, such as by being heated, typically, not morethan 80° C. The coating (13) serves as a sealant to prevent earlydegradation of the organic matter composing the pot.

According to one embodiment a plant pot (10) or other article mayinclude a weakened zone (15) for easy breaking/tearing of the pot (orother article). The weakened zone (15) may include a thinning of the potwall so that the pot may be easily broken or torn along the weakenedzone (15). Other techniques for weakening an area of the pot may beused. According to one embodiment the weakened zone (15) may be locatedon the pot (10) such that the bottom part (12) of the pot may be brokenoff, for example, prior to planting the pot in soil, to enable freegrowth of roots through the bottom area of the pot into the ground.According to other embodiments weakened zones may be located along sidethe pot walls or in any other desired location.

Compositions according to embodiments of the invention enable to coatdifferent areas of a pot in different types of coatings. An example ofthis differential coating is schematically illustrated in FIG. 2.

According to one embodiment the bottom part (22) of a plant pot (20) iscoated by a more durable composition than the surrounding walls (24) ofthe pot. For example, the bottom part (22) of the pot (20) may besubmerged in a first liquid composition comprising a high percent ofpolymer. The liquid composition will reach the inner part of the potthrough the drainage holes (21) and will thus flow over the inner bottompart (22) of the pot. Once the first composition coating the bottom part(22) has dried the surrounding walls (24) of the pot may be coated witha second composition, by spraying or any other suitable method ofapplying a liquid composition. The second composition typicallycomprises a lower percentage of polymer than the first composition.

In another embodiment, the whole pot (20) may be coated by a firstcomposition. Upon drying or upon partial drying, additional coats of thefirst composition (or of another composition) may be applied on thebottom part (22) to achieve a more durable coating of the bottom part(22) than the coating of the rest of the pot.

Having a particularly durable coating on the bottom part of a pot may beuseful especially in cases where seepage irrigation is used.

In other embodiments, the inner part (24 a) of the surrounding walls(24) of a pot (and/or the inner part of the bottom part (22) may besprayed or otherwise coated by a more durable composition than the outerpart (24 b) of the surrounding walls (24). This type of differentialcoating may be especially useful in cases where a plant is watered by adrip or other irrigation system from the top of the pot which wets thesoil in the pot such that the inner parts of the pot are more exposed tomoisture than the outer part of the pot.

According to other embodiments some areas of the pot (20) may be coatedwhile other areas are left uncoated. According to one embodiment aweakened zone (such as weakened zone 15 in FIG. 1) may be coated by adifferent, less durable, composition than other parts of the pot (20).According to other embodiments a zone may be weakened by being leftuncoated or by being coated by a relatively less durable compositionthan other areas of the pot (20).

A composition according to another embodiment of the invention may beused as an adhesive to be mixed in the media of a rooting plug. Asschematically illustrated in FIG. 3, a plug (30) which includes asoilless mix (31) or any other suitable mix, includes a hollow (32) foraccepting a seed, seedling, shoot, grafts or other suitable types ofplants.

Compositions according to embodiments of the invention may be blendedinto the plug mix (31). Upon drying, the composition will conferfirmness to the plug which is advantageous for handling by a mechanicaltransplanter.

In one embodiment, liquid compositions may be sprayed or otherwiseapplied to the hollow (32), to confer rigidity to the structure of thehollow (32).

According to some embodiments plug trays, which are usually made ofplastic, may be made of bio-degradable materials coated by compositionsaccording to embodiments of the invention.

Compositions according to embodiments of the invention may be used infields other than agriculture. For example, the compositions may be usedfor coating bio-degradable disposables such as food ware or table ware.One example of food-ware according to an embodiment of the invention isillustrated in FIG. 4, which shows a plate (42) and cup (44) which arecoated by compositions according to embodiments of the invention.

Bio-degradable plates or cups may be made of organic materials such assugar cane and/or other starches. Durability of plates, cups and otherbio-degradable table-ware may be strengthened by being coated withcompositions according to embodiments of the invention, therebyenhancing their shelf-life without diminishing their friendliness to theenvironment.

Embodiments of the invention will be exemplified in the following nonlimiting examples.

EXAMPLES

Compositions I-VIII were prepared by mixing PLA resin (Ingeo™ byNatureWorks, USA) into a mixture of solvents at room temperature (about25° C.) until full dissolution of the resin. Resulting compositions werefluid, in different levels of viscosity. Viscosity of each compositionwas directly proportional to the percent of polymer in the composition.

Example 1 Rooting Plugs Composition I:

-   lgr PLA-   40 ml EtOAc-   10 ml DCM

Rooting plugs of 2×3 cm were prepared using an Ellegaard™ system. Afinger sized hollow was made in the center of each plug. Each hollow wassprayed with 0.5 cc of composition I using a syringe. Control plugs wereleft untreated. The plugs were dried in RT over night and a Gypsophila(Baby's Breath) shoot was placed in each of the plugs' hollows. Plugswere irrigated for one month with irrigation from on top.

Plant Development—Plant development was better in treated plugs. Plantsgrown in treated plugs had more root mass than the plants grown incontrol plugs, possibly due to better water retention in the treatedplugs.

Composition stability—Treated plugs were stable after one month intrays. Degradation of treated plugs was observed upon planting in soil(within days of planting).

Composition II

-   0.5 gr PLA-   35 ml EtOAc-   10 ml DCM-   5 ml acetone

Rooting plugs of 2×3 cm were prepared using an Ellegaard™ system. Afinger sized hollow was made in the center of each plug. Each hollow wassprayed with 0.5 cc of composition II using a syringe. Control plugswere left untreated. The plugs were dried over night. A tomato plant wasplaced in each plug's hollow. Plugs were irrigated for two weeks withirrigation from on top.

Plant Development—Plant development was better in treated plugs asdescribed above.

Composition stability—Treated plugs were stable for two weeks in trays.Degradation started after two weeks.

Similar results are expected with all types of vegetables and othershort term plants.

Example 2 Bio-Degradable Plant Pots

Composition III: Composition IV: Composition V: 4 gr PLA 4 gr PLA 4 grPLA 160 ml EtOAc 180 ml EtOAc 160 ml EtOAc 40 ml DCM 20 ml DCM 20 ml DCM20 ml acetone

Plant pots (7 cm diameter, made of packed saw dust (50%) and starch(50%) ) were immersed in compositions III-V until totally coated. Thepots were let to air dry at RT for 30-45 minutes. Coated pots werefilled with soil (mostly peat). A shoot of mint plant was planted in thesoil filled pots. Pots were irrigated once a day such that the soil wasalways moist, for three months. The pots were buried in soil after threemonths.

In addition to using the compositions to coat the pots, compositionswere also left to dry in the beaker to examine their differentcharacteristics when dried films.

Plant Development—no negative effect was demonstrated on growth of themint plants.

Composition stability—composition IV dried to form a more elastic filmthan composition III. Composition V could be diluted in water as opposedto compositions III and IV which could not be easily dissolved in water.

Coated plant pots were stable for three months. After being buried insoil for two days the framework of the pots began to deteriorate. Afterthree days of being buried in soil the pot framework was completelydisintegrated.

Composition VI: Composition VII 12 gr PLA 20 gr PLA 100 ml EtOAc 100 mlEtOAc 100 ml DCM 100 ml DCM

Plant pots (7 cm diameter, made of packed saw dust (50%) and starch(50%) ) were immersed in compositions VI-VII until totally coated. Thepots were let to air dry at RT for an hour. Some of the pots were coatedtwice. Coated pots were filled with soil (mostly peat). A shoot of mintplant was planted in the soil filled pots. Pots were irrigated once aday such that the soil was always moist, for over three months. The potswere buried in soil after more than three months.

Plant Development—no negative effect was demonstrated on growth of themint plants.

Composition stability—Plant pots coated with composition VI were stablefor three months. Plant pots coated with composition VII were stable forover three months. After being buried in soil for two days the frameworkof all the pots began to deteriorate. After three days of being buriedin soil the pot framework was completely disintegrated. The pots havingtwo layers of coating disintegrated only after being buried for 5-6days.

Example 3 Bio-Degradable Plates Composition VIII:

-   0.1 gr PLA-   45 ml EtOAc-   5 ml DCM

Paper plates coated with composition VIII are expected to have a longshelf life and to disintegrate a few days after being continuouslyexposed to moisture (e.g., the environment in a garbage dump). CLAIMS

1. A method for preparing a rooting plug, the method comprising mixing acomposition comprising (i) 0.2%-10% w/w bio-degradable polymer and (ii)an organic non-hydroxylic solvent with a plug mix, thereby preparing arooting plug.
 2. The method of claim 1, comprising creating a hollow inthe plug mix and mixing the composition with the plug mix at the hollow.3. The method of claim 1, wherein the organic non-hydroxylic solvent hasa boiling point of less than 80° C.
 4. The method of claim 1, whereinthe composition comprises a plurality of organic non-hydroxylicsolvents.
 5. The method of claim 1, wherein the composition comprises amixture of solvents, one solvent having a higher boiling point than theother.
 6. The method of claim 4, wherein one of the organicnon-hydroxylic solvents is an organic ester or a ketone.
 7. The methodof claim 1, wherein the organic non-hydroxylic solvent is selected fromthe group consisting of dichloromethane (DCM), dichloroethane,tetrachloroethylene, tetrahydrochloride, dimethylformamide (DMF),acetonitrile, dimethyl sulfoxide (DMSO).
 8. The method of claim 1,wherein the organic non-hydroxylic solvents is an organic ester selectedfrom ethyl acetate (EtOAc), butyl acetate and ethyl propionyl.
 9. Themethod of claim 1, wherein the organic non-hydroxylic solvents is aketon selected from acetone and cyclohexanone.
 10. The method of claim1, comprising 0.2%-10% w/w PLA, up to 50% of an organic ester and up to50% keton.
 11. The method of claim 1, comprising 0.2% -1% w/wbio-degradable polymer.
 12. The method of claim 1, wherein thecomposition comprises 1-2% w/w bio-degradable polymer.
 13. The method ofclaim 1, comprising about 6% w/w bio-degradable polymer.
 14. The methodof claim 1, wherein the bio-degradable polymer is a polyester.
 15. Themethod of claim 1, wherein the bio-degradable polymer is selected frompolylactic acid (PLA), poly lactic-co-glycolic acid (PLGA).
 16. Themethod of claim 1, wherein the bio-degradable polymer is in a form of aresin.
 17. The method of claim 1, comprising about 10% w/wbio-degradable polymer.
 18. The method of claim 1 for the preparation ofa bio-degradable plant pot.
 19. A bio-degradable article prepared by themethod of claim 1.